Vista - Can't Change Workgroup Name

I have a Vista PC and an XP PC and on the Vista PC, I can not change the
Workgroup to the name of my home workgroup. I get an network error message
when I click on the Apply button. There are no special characters or spaces
in my home workgroup name. What's interesting is that when I do a Query of
the Network computers on the Vista PC, I can navigate to the folders that
are shared on the XP PC. The problem I'm having is that I am trying to share
a printer that is physically connected to the XP machine with the Vista PC.

Even though both PC's are on the same physical network but on different
Workgroups, I can see my XP machine, which I thought was not possible, if
you're on two different workgroups. I have temporarily turned off the
Firewall on both computers, but I get the same network error message.